Shift and shift lock and release mechanisms, which are known as secretarial shift mechanisms, are commonly employed on keyboards. The mechanisms are often unduly complex and result in excessive manufacturing and assembly costs. One attempt of reducing the complexity of such keyboards is described in U.S. Pat. No. 4,071,719, which issued Jan. 31, 1978, in the name of Robert Christen Madland and which is assigned to the assignee of the present invention. The keyboard of the Madland patent was a substantial improvement in reducing the complexity of such mechanisms since it required only a single elongated connecting rod between the keyswitches. However, the Madland keyboard did require that the keyboard employ the shift and shift lock keyswitches which required the addition of slideable cam followers on the top of the housing of the keyswitch and which were actuated by a cam that was formed on the plunger of the keyswitch. Thus, while the keyboard of the prior Madland patent substantially reduced the assembly cost of a secretarial shift mechanism, since the cost was essentially the same as the cost of inserting three standard keyswitches into the keyboard, this design still required the manufacture of special keyswitches that were more complex than desired.
The present invention, by contrast, may utilize keyswitches that are basically the same as the other keyswitches of the keyboard, for both the shift and shift lock release functions. In the case of the shift keyswitch it is only required to add a generally T-shaped actuating bar to the plunger of the basic keyswitch of the keyboard. For the shift lock and release keyswitch it is necessary only to add a generally C-shaped retaining spring around the housing of the basic keyswitch of the keyboard. The shift and shift lock and release keyswitches correspond generally to those of U.S. Pat. No. 4,227,163 issued Oct. 7, 1980 in the name of Raymond Barnoski, entitled "Electrical Keyswitch" and assigned to the assignee of the present invention. A pair of retaining wedges support are required on the outer housing of the shift lock and release keyswitch for the wire spring retainer. In addition, slots are required in the housing of the keyswitches of the present invention that are not needed by the switches of U.S. Pat. No. 4,227,163 to allow for the latching finger on the shift lock and release keyswitch (hereafter called the shift lock keyswitch for short) and for movement of the T-shaped actuating bar on the shift keyswitches. However, these features may merely be provided on all keyswitches of the keyboard if desired and the only additional features that would then be required for the shift and shift lock keyswitches are the T-shaped bars and the C-shaped wire spring retainer.